Various types of material handling apparatus include metal surfaces which are subject to excessive wear. For example, the movement of rocks and gravel (e.g. in chutes or hoppers) against metal involves significant impact and friction which results in excessive wear.
The use of rubber and urethane pads fastened to metal surfaces to protect against abrasion and impact is known. For example, in my prior patent (U.S. Pat. No. 5,735,377) I describe a system in which impact or wear pads are bolted to a desired wear surface with bolts which are not exposed on the wear side of the pad. Although that system is very useful in reducing wear, the time and effort required for drilling the required holes is considerable.
Other prior systems use a roll or flat sheet of rubber or urethane which must be field cut to size, and holes must be cut in the rubber or urethane to align with holes in the metal to be protected. This is cumbersome and time-consuming.
Complicating the repair process is the fact that the chutes or hoppers are normally located several feet above the ground and are inclined at an angle to facilitate gravity flow of material (such as gravel or crushed rock) through the chute or hopper. For example, a chute is normally attached to the discharge end of a screen frame to direct discharged material onto a conveyor belt for transportation to other areas. The size of the material being discharged varies from large rocks to fine processed sand.
The top end of the chute liner is as wide as the screen deck from which it is receiving material. The bottom end of the chute is typically 2 to 4 feet wide, and the bottom end is narrower than the top end in order to concentrate the material from spilling out over the sides of the conveyor belt.
Gravel screens are always located at least 16 feet above the ground, and sometimes they are several stories in height. The reason for this is because the material being screened falls downwardly due to gravity each time it is processed. The chutes are attached to the screen deck and are thus located high off the ground. Thus, the accessibility for servicing the chutes is very difficult.
The crushed rock and sand traveling through the chute or hopper, etc. causes severe wear on the chute, hopper, etc. As a result, the bottom and side surfaces of the chute, etc. must be in good repair in order to prevent granulated material from leaking through holes in the bottom or side surfaces.
These chutes come in various lengths and widths. They are generally about 6 to 8 feet wide at the top and 2 to 4 feet wide at the bottom end. The length may vary from about 5 to 12 feet.
One present method for repairing a worn chute involves removing the chute from the screen deck and lowering it to the ground to remove worn liner sections and install new sections. This procedure may be impractical if it would cause the entire screening operation to shut down. Also, the use of cranes or other such equipment would be required. Concerning the repair itself, if an entire new liner is built for replacing the worn existing liner, this would be very expensive.
The use of urethane or rubber impact-resistant panels in screen decks has been known. The panels are held in place on a frame which is welded to the surface to be protected. The frame is normally supplied by the manufacturer as one long section which is cut to length (as required for a particular location in a particular deck, for example). The first section of frame is cut to required length and then welded to the metal surface to be protected. Then another length of frame is measured, cut and welded to the metal surface at a measured precise distance from the first frame section. This is critical because the impact-resistant panels to be attached to the frame have a predetermined width, and the adjacent frame sections must be precisely located in order to be able to frictionally engage the opposing side edges of the impact-resistant panels and hold them in place without the use of any fasteners or other hardware. Thus, the spacing of adjacent frame sections is critical and must be within about 1/16 inch or less in order to properly receive and hold the impact-resistant panels during use.
The procedure of measuring the required length of the next frame piece, cutting it to length, measuring its proper location relative to the preceding frame piece, and welding it into place is repeated until the entire length of the screen deck has been covered. After all of the frame pieces have been properly installed, the individual impact-resistant panels are installed on the frame.
The foregoing snap-in impact-resistant panels have not been used in chutes, hoppers, etc. because of (a) poor accessibility to the chute itself (if the chute protrudes from the back of the screen deck and is inclined), and (b) the width of the chute is not standard (the width at the top end varies from 5 to 8 feet and the width at the bottom end is 2 to 4 feet; the length may vary from about 4 to 12 feet). These conditions make it extremely difficult to use a snap-in panel. It is very difficult to measure and weld frame sections to the surfaces of an inclined chute and achieve the required tolerance.
There has not heretofore been provided a system having the features and advantages provided by the present invention.